Heat sink assembly for electronic equipment

ABSTRACT

A heat sink assembly for a cage for a field replaceable computing module includes a heat sink, a thermal interface material (TIM), and an actuation assembly. The heat sink includes a mating surface. The TIM includes a first surface that is coupled to the mating surface and a second surface that is opposite the first surface. Thus, the second surface can engage a heat transfer surface of a field replaceable computing module installed adjacent the heat sink. The actuation assembly includes a shape memory alloy (SMA) element. When the SMA element is in a first position, the second surface of the TIM contacts the heat transfer surface of the computing module. When the SMA element moves to a second position, the second surface of the TIM is moved a distance away from the heat transfer surface of the computing module.

TECHNICAL FIELD

The present disclosure relates to high performance and/or high densitycomputing solutions, such as line cards and computing blades, that canreceive field replaceable computing modules, and in particular to a heatsink assembly for these computing solutions.

BACKGROUND

Over the past several years, the information technology field has seen atremendous increase in the performance of electronic equipment coupledwith a decrease in geometric floor space to house the equipment. Forinstance, due at least to recent advances in high throughput computing,field replaceable computing modules, such as optical transceivers, aredissipating more power (e.g., 25 Watts (W) or more) in smaller formfactors (i.e., computing modules are being provided with increasinglyhigher power densities). However, permissible operating temperatures,which may be defined by temperature limits of internal componentsincluded in the field replaceable computing modules, have remainedrelatively stagnant. Moreover, as computing solutions become denser,less space is available for cooling solutions. Thus, cooling solutionsfor field replaceable computing modules that can provide improvedcooling in smaller form factors are continuously desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram illustrating a sectional view of anexample embodiment of a heat sink assembly formed in accordance with thepresent application.

FIG. 1B is a diagram illustrating heat transfer between a fieldreplaceable computing module and conventional heat sinks.

FIG. 2A illustrates a front perspective view of an example embodiment ofa computing solution that includes an example embodiment of the heatsink assembly presented herein.

FIG. 2B illustrates a field replaceable computing module included in thecomputing solution of FIG. 2A.

FIG. 3A illustrates a front perspective view of a computing apparatus ofthe computing solution of FIG. 2A with its top cover removed to show theheat sink assembly included therein.

FIG. 3B illustrates a front perspective view of a module cage includedin the computing apparatus of FIG. 3A, according to an exampleembodiment.

FIG. 3C illustrates a bottom perspective view of an example embodimentof a heat sink that may be included in the heat sink assembly of FIG.3A, according to an example embodiment.

FIG. 4 illustrates a top, front perspective view of the heat sinkassembly and module cage included in the computing apparatus of FIG. 3A.

FIG. 5 illustrates an exploded view of the heat sink assembly includedin the computing apparatus of FIG. 3A.

FIG. 6 is a diagram that schematically illustrates circuitry that may beincluded in the heat sink assembly of FIG. 3A, according to an exampleembodiment.

FIG. 7 is a side view of a shape memory alloy (SMA) element that may beincluded in the heat sink assembly of FIG. 3A, according to an exampleembodiment.

FIG. 8 illustrates a front perspective view of a portion of an exteriorof the computing apparatus of FIG. 3A, according to an exampleembodiment.

FIG. 9 is a flow chart depicting a method for operating components of anexample embodiment of a heat sink assembly of the present application.

FIG. 10A illustrates a side, sectional view of another exampleembodiment of a heat sink assembly, the heat sink assembly being in alowered position.

FIG. 10B illustrates a side, sectional view of the heat sink assembly ofFIG. 10A while in a raised position, according to an example embodiment.

FIGS. 11A and 11B illustrate perspective views of a heat sink and afield replaceable computing module, respectively, with which the heatsink assembly presented herein may be utilized, according to anotherexample embodiment.

FIG. 12 illustrates a side, sectional view of another example embodimentof the heat sink assembly presented herein.

FIG. 13 illustrates a top perspective view of still another exampleembodiment of the heat sink assembly presented herein.

FIGS. 14A and 14B illustrate side, sectional views of yet anotherexample embodiment of a heat sink assembly that may be included in thecomputing solution of FIG. 2, the heat sink assembly being illustratedin a lowered position in FIG. 14A and a raised position in FIG. 14B.

FIGS. 15A and 15B are side views of a shape memory alloy (SMA) elementthat may be included in the heat sink assembly of FIGS. 14A and 14B,according to an example embodiment.

FIGS. 16 and 17 illustrate front perspective views of exampleembodiments of computing solutions and computing modules with which theheat sink assembly presented herein may be utilized.

FIG. 18 is a diagram illustrating thermal advantages provided by theheat sink assembly presented herein.

Like reference numerals have been used to identify like elementsthroughout this disclosure.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

A heat sink assembly for a cage for a field replaceable computingmodule, an apparatus including the cage, and a system including theapparatus and the field replaceable computing module are presentedherein. In one embodiment, a heat sink assembly for a cage for a fieldreplaceable computing module includes a heat sink, a thermal interfacematerial, and an actuation assembly. The heat sink facilitates heatdissipation and includes a mating surface. The thermal interfacematerial includes a first surface that is coupled to the mating surfaceof the heat sink and a second surface that is opposite the firstsurface. Thus, the second surface can engage a heat transfer surface ofa field replaceable computing module installed adjacent to the heatsink. The actuation assembly includes a shape memory alloy (SMA)element. When the SMA element is in a first position, the second surfaceof the thermal interface material contacts the heat transfer surface ofthe field replaceable computing module, and when the SMA element ismoved to a second position, the second surface of the thermal interfacematerial is moved a distance away from the heat transfer surface of thefield replaceable computing module.

Example Embodiments

The heat sink assembly presented herein enables high performance and/orhigh density computing solutions, such as line cards and computingblades, to effectively dissipate heat from field replaceable computingmodules without inhibiting insertion or removal of the field replaceablecomputing modules (also referred to herein as “modules,” “pluggablemodules,” “swappable modules,” and the like), such as during onlineinsertion and removal (“OIR”) operations. Specifically, the heat sinkassembly presented provides a movable or “floating” heat sink and anactuation assembly that can move the floating heat sink towards and/oraway from a module cage included in a computing solution.

Notably, the heat sink assembly presented herein may be primarilyactuated via an electrical actuation. Thus, the actuator may occupy aminimal amount of space on a front panel of a computing solution, whichmay be beneficial, if not required, for computing solutions with densefront panel layouts. In fact, in some instances, the heat sink assemblypresented herein may be actuated via a purely electrical actuation(i.e., only an electrical actuation). In these instances, the heat sinkassembly need not include a physical/mechanical actuator. That is, in atleast some instances, the heat sink assembly may eliminate any need fora physical/mechanical actuator. Regardless, the heat sink assemblypresented herein can also lock a heat sink in a raised position or alowered position, which may simplify insertion and removal of a module.This locking may also allow that the heat sink assembly presented hereinto compress a heat sink and a thermal interface material (“TIM”)included thereon against a module.

Moreover, in at least some embodiments, the actuation assembly moves theentire heat sink away from the module cage (and/or a module installedtherein), thereby reducing, if not eliminating, the risk of a modulescraping against the heat sink assembly during insertion or removaloperations. In fact, the actuation assembly may move the heat sink sothat the mating surface of the heat sink (e.g., a bottom surface)remains parallel to a heat transfer surface of a module (e.g., a topsurface). Consequently, during insertion or removal of the module, theentire mating surface of the heat sink (e.g., the bottom surface) willbe equally spaced apart from the heat transfer surface of the module(e.g., the top surface) by a gap and the module will not rub or slideagainst the mating surface of the heat sink. This gap, in turn, allows aTIM, which would be damaged by sliding or rubbing, to be included on themating surface. The TIM increases thermal conductivity between the heatsink and a module and, thus, improves cooling for the module.Additionally, parallel motion of the heat sink with respect to themodule cage may provide a substantially consistent gap between theheatsink and the module, which may allow the gap required for moduleremoval to be minimized.

Additionally or alternatively, the actuation assembly may move the heatsink along one degree of freedom (e.g., vertically). Moving the heatsink along one degree of freedom (e.g., vertically) may ensure that theheat sink does not need to be positioned adjacent open space, which isnecessary when a heat sink moves in a lateral or depth direction (e.g.,a front-to-back direction). Instead, the surface area of the heat sinksize may be maximized to span a perimeter of a module and/or module cageand the cage need not be positioned with open space surrounding itsperipheral boundaries. That is, moving the heat sink along one degree offreedom may maximize a thermal contact area. Furthermore, moving theheat sink along one degree of freedom may allow the heat sink togenerate compression forces on a TIM (e.g., if the one degree of freedomis linear, vertical movement) that are often necessary to maximize TIMperformance with the assembly that moves the heat sink. This may reducethe number of components in the assembly, reducing costs of manufactureand servicing. The TIM also tends to reduce, if not eliminate, theeffects of minor dimensional differences between different pluggablemodules.

In order to describe the heat sink assembly, computing apparatus, andcomputing system presented herein, terms such as “left,” “right,” “top,”“bottom,” “front,” “rear,” “side,” “height,” “length,” “width,” “upper,”“lower,” “interior,” “exterior,” “inner,” “outer,” “depth,” and the likeas may be used. However, it is to be understood that these terms merelydescribe points of reference and do not limit the embodiments to anyparticular orientation or configuration. For example, the terms“height,” “width,” and “depth” may be used to describe certainembodiments presented herein, but it is to be understood that theseterms are not intended to limit the present application to specificimplementations. Instead, in at least some embodiments, the heat sinkassembly presented herein may be oriented horizontally (as shown) orvertically (i.e., a housing of a computing solution may be rotated 90degrees about an axis extending through a front and back of thehousing), or in any other manner during use (e.g., when installed into ablade chassis/enclosure). Consequently, even if a certain dimension isdescribed herein as a “width,” it may be understood that this dimensionmay provide a height or depth when a computing solution in which it isincluded is moved to different orientations.

Now turning to FIG. 1A, this Figure schematically illustrates an exampleembodiment of a computing solution 10 that includes an exampleembodiment of the heat sink assembly 30 presented herein (forsimplicity, at least some components of the heat sink assembly 30 arenot shown in FIG. 1A). The computing solution 10 may also be referred toas a computing system; however, it is to be understood that the term“system,” when used herein, does not imply that the solution/system 10is a stand-alone system. Instead, a solution/system 10 may be astand-alone system or a portion/subsystem of a larger system (e.g.,solution 10 may be a blade of a server). That said, in FIG. 1A, thecomputing solution 10 includes an apparatus 12 and a removable computingmodule 20. The apparatus 12 includes a housing 14 that houses a PCB 16and a module cage 18 (e.g., an optical cage). Additionally, the housing14 houses a heat sink assembly 30 with a heat sink 31 and a thermalinterface material (TIM) 35. The TIM 35 is included on a bottom ormating surface of the heat sink 31 and, as is depicted, during insertionor removal of the computing module 20 into the module cage 18, the heatsink assembly 30 moves the heat sink 31 and TIM 35 away from the modulecage 18 to provide a gap “G” between the computing module 20 and the TIM35.

In the depicted embodiment, the heat sink assembly 30 moves the heatsink 31 and the TIM 35 upwards. More specifically, the heat sinkassembly 30 moves the entire heat sink 31 and entire TIM 35 upwards,away from the module cage 18. In at least some embodiments, the heatsink assembly 30 moves the heat sink 31 and TIM 35 while keeping the TIM35 parallel to a top of the module cage 18. Alternatively, the heat sink31 and TIM 35 might be moved upwards in any manner, but are moved into araised position that is parallel to a top of the module cage 18. Stillfurther, in some embodiments, the TIM 35 is not parallel to the top ofthe module cage 18 when in a raised position, but is spaced apart fromthe top of the module cage 18 across its surface area (e.g., so that thegap G spans the whole TIM 35). Regardless of how the heat sink 31 andTIM 35 are moved to a raised position (and regardless of how the TIM 35is oriented in its raised position), the gap G allows the computingmodule 20 to be inserted into or removed from module cage 18 withoutcontacting and damaging TIM 35. If, instead, only a portion of the TIM35 was moved away from the module cage 18 (e.g., if the heat sinkassembly 30 was tipped about a lateral axis, which would extend into theplane of the drawing sheet on which FIG. 1A is included), the computingmodule 20 might contact and damage the TIM 35 (e.g., by scraping aportion of the TIM 35 off of the heat sink assembly 30).

Alternatively, and now turning to FIG. 1B, if the heat sink assembly 30does not include a TIM 35, a metal surface of a heat sink 31 included inthe heat sink assembly 30 might not form an effective thermal connectionwith the computing module 20. For example, since metal surfaces (e.g., abottom of a heat sink and/or top of a module) can have surfaceirregularities, such as flatness irregularities, wavinessirregularities, roughness irregularities, etc., air gaps may formbetween the metal surfaces of a heat sink 31 and a computing module 20.In FIG. 1B, the left image illustrates air gaps AG1 that form betweenmetal surfaces with surface flatness irregularities while the rightimage illustrates air gaps AG2 that form between metal surfaces withsurface roughness irregularities. Notably, many riding heat sinks, whichare often biased into contact with a module via spring clips that pressthe heat sink against a module during insertion or removal, provideinefficient heat transfer away from computing modules 20 due to air gapissues. These issues cannot be remedied by a TIM 35, because the TIMwould be scraped off or otherwise damaged as a heat sink “rides” on asliding module. Regardless of how air gaps form between the module 20and the heat sink assembly 30, air gaps are detrimental to heat transferbecause the low thermal conductivity of air provides significant contactresistance. A TIM can reduce or eliminate these air gaps andsignificantly reduce contact resistance, especially if the TIM iscompressed to a specific compression to maximize heat transfer (whichmay differ for different materials).

FIG. 2A illustrates a top perspective view of a computing apparatus 12and a replaceable computing module 20 that may be installed within theapparatus 12 to form a computing solution 10. As is shown, the computingapparatus 12 includes a front surface or panel 100 with an opening 101that provides access to the module cage 18 defined therein. In thedepicted embodiment, the module cage 18 extends in a depth direction(e.g., front-to-back) within the housing 14 of the apparatus 12. Thatis, the module cage 18 extends from the front panel 100 towards a backend 102 of the housing 14. Additionally, in the depicted embodiment, themodule cage 18 is arranged to be substantially flat within the housing14, such that the module cage 18 is parallel to a cover 104 that definesa top of the housing 14.

Meanwhile, and now referring to FIG. 2A in combination with FIG. 2B, themodule 20 includes a top surface 22, a back surface 24 with a connector25, a bottom surface 26, and a front surface 28. As is discussed infurther detail below, in the depicted embodiment, the top surface 22 ofthe computing module 20 is a heat transfer surface for the computingmodule 20. However, in other embodiments, any surface of the computingmodule 20 could serve as a heat transfer surface. During insertion ofthe computing module 20 into the module cage 18, the perimeter of backsurface 24 is aligned with the module cage 18 and then the computingmodule 20 is pushed into the module cage 18 to connect the connector 25on the back surface 24 with a connector 124 included in the module cage18 (see FIG. 3B). During removal of the computing module 20 from themodule cage 18, the front surface 28 may be grasped, e.g., by handle 29,and pulled out of the module cage 18. However, handle 29 is merelyrepresentative of a feature that enables a user to easily grasp thefront surface 28 and, in other embodiments, the module 20 could includeany other features instead of or in addition to handle 29.Alternatively, the computing module 20 can be ejected or removed fromthe module cage 18 in any manner now known or developed hereafter(including mechanical ejections). Before or after the computing module20 is installed in the module cage 18, the housing 14 may be installedinto another computing solution (e.g., a rack) and secured thereto withinstallation member 112 (see FIGS. 2A and 3A).

In FIG. 2A (as well as many other Figures), the computing solution 10 isa line card; however, it is to be understood that a line card is simplyone example of a computing solution in which the heat sink assemblypresented herein may be included. For example, the computing solution 10could also be a rack server, a storage drawer, a stand-alone computingsolution, or any other computing solution that accepts modular computingcomponents (e.g., “field replaceable computing modules”). Likewise, inFIGS. 2A and 2B (as well as many other Figures), the module 20 is anoptical transceiver, but it is to be understood that an opticaltransceiver is simply one example of a module with which the heat sinkassembly presented herein may be used. That said, it may be beneficialto utilize the heat sink presented herein with optical transceiversbecause technical advancements in optical transceivers have generatedhigh power dissipation (e.g., 25 W or more) in a small form factor(e.g., C form-factor pluggable 2 (“CFP2”) form factor, which hasdimensions of 41.5 millimeters (“mm”)×12.4 mm×107.5 mm (w×h×d)). Thesecharacteristics make it difficult to satisfy Network Equipment-BuildingSystem (NEB S) thermal standards for these modules.

Now turning to FIGS. 3A, 3B, and 3C, these Figures illustrate portionsof the apparatus 12 in further detail. In FIG. 3A, the apparatus 12 isshown with its top cover 104 removed. With the top cover 104 removed,the heat sink assembly 30 can be seen disposed above the module cage 18.Meanwhile, FIG. 3B illustrates the module cage 18 removed from thehousing 14 and FIG. 3C illustrates a heat sink 31 of heat sink assembly30 removed from the apparatus 12. As can be seen in FIG. 3B, the modulecage 18 extends from an open front end 120 to a back end 122. The backend 122 includes a connector 124 that may connect a computing module 20to an apparatus 12 in which the module cage 18 is included (e.g., viaPCB 16). That is, the connector 124 may be configured to provide a SmallComputer System Interface (SCSI) connection, Serial Attached SCSI (SAS)connection, an advanced technology attachment (ATA) connection, a SerialATA (SATA) connection, and/or any other type of connection for fieldreplaceable computing modules.

Additionally, the module cage 18 extends from a first side 126 to asecond side 128 and includes an open top 130. Collectively, the openfront end 120, the back end 122, the first side 126, the second side128, and the open top 130 define an internal chamber 132. That is, theopen front end 120, the back end 122, the first side 126, the secondside 128, and the open top 130 define a perimeter or periphery ofchamber 132 (with sides 126 and 128 defining a lateral periphery whilefront end 120 and back end 122 defining a longitudinal periphery). Thechamber 132 is sized to house/receive computing module 20 and the opentop 130 allows the heat sink assembly 30 to access and engage the topsurface 22 (i.e., the heat transfer surface) of a computing module 20installed within a chamber 132.

In different embodiments, the open top 130 may provide access to thechamber 132 in any desirable manner, such as via one or more windows,cut-outs, segments, etc. However, in the depicted embodiment, the opentop 130 spans the entire surface area of the chamber 132, extending alength L1 from the open front end 120 to the back end 122 (e.g., in afront-to-back or depth dimension) and a width W1 from the first side 126to the second side 128 (e.g., in a lateral or width dimension). Thus,the depicted embodiment may maximize the area within which heat maytransfer from the computing module 20 to the heat sink assembly 30.

In FIG. 3C, the heat sink 31 is shown from a bottom perspective view,which illustrates the TIM 35 that is included on a mating surface 133 ofthe heat sink 31. The TIM 35 includes a first surface 135 and a secondsurface 136. The second surface 136 is fixedly coupled to the matingsurface 133 of the heat sink 31 (e.g., via adhesive, ultrasonic welding,etc.) and the first surface 135 is disposed opposite the second surface136. Thus, the first surface 135 faces the open top 130 of the modulecage 18 when the heat sink 31 is installed above the module cage 18. Inat least some embodiments, the first surface 135 may include or becoated with a protective film that prevents the first surface 135 fromsticking to a module 20. In the depicted embodiment, the first surface135 and second surface 136 converge towards both a front 144 and a back146 (see FIG. 5) of the heat sink 31 so that the second surface 135includes convergent sections 137 and a flat section 138. However, inother embodiments, the first surface 135 and the second surface 136 neednot converge and, for example, may be parallel to each other across thedimensions of the TIM 35.

Regardless of the shape of the TIM 35, the mating surface 133 of theheat sink 31 may have dimensions L2 (e.g., a front-to-back dimension)and W2 (e.g., a width) that are at least as large as the correspondingtop dimensions (L1 and W1, respectively) of the chamber 132 (defined bythe open top 130) and a heat receiving portion of the TIM 35 (e.g., theflat section 138) may span or cover a majority of the mating surface133. More specifically, the TIM 35 may span (e.g., cover) at least adepth or front-to-back dimension L1 of the open top 130 (which defines adepth of a top of the chamber 132). Additionally or alternatively, theTIM 35 may span a lateral dimension L2 of the open top 130 (whichdefines a lateral dimension of a top of the chamber 132). For example,the flat section 138 of the TIM 35 may have a lateral dimension W3(e.g., width W3) that is equal to or greater than W1 and/or the flatsection 138 of the TIM 35 may have a front-to-back dimension L3 (e.g.,depth L3) that is equal to or greater than L1. Consequently, the flatsection 138 of the TIM 35 may cover as much of the computing module 20as possible and maximize heat transfer between a computing module 20 andthe heat sink 31.

Notably, with the heat sink assembly presented herein, the TIM 35 canspan the entire surface area (e.g., L1 by W1) of the chamber 132because, in at least some embodiments, the heat sink assembly 30 onlymoves the heat sink 31 vertically with respect to the module cage 18(and a computing module 20 installed therein). If, instead, the heatsink 31 moved laterally or in a front-to-back direction, open spacewould need to be available to allow movement of heat sink 31. In someinstances, this issue might be addressed by moving the heat sink 31outside the peripheral boundaries of the module cage 18 (e.g., laterallybeyond side 126 or 128). However, such movement would increase thedimensional footprint of the heat sink assembly 30, which is oftenundesirable, if not impossible, in high-density computing solutions.

Still referring to FIG. 3C, the mating surface 133 of the heat sink 31forms a bottom of the heat sink 31 and fins 140 extend upwardstherefrom. Specifically, the fins 140 and/or the mating surface 133 mayinclude/define a base 142 and the fins 140 may extend from the base 142to a top 143 of the heat sink 31. In the depicted embodiment, the fins140 cover a majority of the base 142 between a front 144 and a back 146of the heat sink 31 to maximize cooling and each of the fins 140 extendsin a side-to-side direction across the heat sink 31. However, in otherembodiments, the fins 140 may be arranged in any orientation orconfiguration. For example, the fin geometry, profile, and dimensionscan be customized for different types of applications and airflowdirections (e.g., front-to-back and/or side-to-side airflow). Stillfurther, in yet other embodiments, heat sink 31 might be finless andmay, for example, dissipate heat via heat pipes, fluid thermalmanagement, or other mechanisms/arrangements that dissipate heat.

Now turning to FIGS. 4 and 5, the fins 140 may also define a number ofopenings, cavities, channels, mounting features, etc. to accommodate andsecure portions of the heat sink assembly 30, such as an actuationassembly 150 of the heat sink assembly 30. In the depicted embodiment,the fins 140 define a passageway 152 that extends in a front-to-backdirection through the heat sink 31 and also define three mounting points154 spaced along top edges of the passageway 152 (i.e., at a top ofsides of the passageway 152). The passageway 152 is an open-toppassageway that is centered with respect to the fins 140, but in otherembodiments, the passageway 152 could be a through hole, a partiallycovered passageway, or any other opening/passageway/cavity. Additionallyor alternatively, in other embodiments, the passageway 152 need not becentered with respect to the fins 140 and/or could be one of a pluralityof passageways. Moreover, although not shown, in some embodiments thefins 140 may define additional channels configured to accommodate otherfeatures or elements, such as longitudinal channels for guide pins thatextend fully or partially through the fins 140. Still further, in someembodiments the fins 140 need not define any openings, cavities,channels, etc. For example, the actuation assembly 150 might extendalong one or more sides of heat sink 31 (such an actuation assembly 150might have a height that is low enough not to impair airflow through theheat sink 31).

Generally, and still referring to FIGS. 4 and 5, the heat sink 31 ispositioned atop the cage 18, but is not directly connected to the modulecage 18. Instead, the heat sink 31 is “floating” with respect to themodule cage 18 and the actuation assembly 150 movably couples the heatsink 31 to the module cage 18. That is, the actuation assembly 150included in the heat sink assembly 30 presented herein is configured tolift and lower the heat sink 31. In the embodiment of FIGS. 2A-5, theactuation assembly 150 includes a biasing member 160, a shape memoryalloy (SMA) element 172, and closure brackets 180. Additionally, in thedepicted embodiment, the heat sink assembly 30 includes a support frame190 that helps couple the actuation assembly 150 to the module cage 18.

In the depicted embodiment, the biasing member 160 is connected themodule cage 18 via connectors 166 and includes spring members 164 thatare positioned above the base 142 of the heat sink 31. Specifically, thespring members 164 engage corners 145 of a top surface of the base 142of the fins 140, which are left open by shortened fins 140 disposed at afront 144 and back 146 of the heat sink 31. The spring members 164 areconnected together by support members 162 and, since the biasing member160 is anchored to (i.e., fixedly coupled to) the module cage viaconnectors 166, the spring members 164 resist upwards movement of theheat sink 31. Thus, the spring members 164 exert a restorative force onthe heat sink 31 in response to upwards movement of the heat sink 31.That is, due to the aforementioned features and connections, the biasingmember 160 will consistently urge the heat sink 31 towards the modulecage 18. However, biasing member 160 is only one example of an element,structure, and/or feature that may return the SMA element 172 to a restor engaged position on or adjacent to the module cage 18 and, in otherembodiments, SMA element 172 may be returned to its rest or engagedposition in any desirable manner. In fact, other example techniques orelements are discussed in further detail below.

Meanwhile, the SMA element 172 includes a proximal end 174, a distal end176, and an elongate section 178 extending between the proximal end 174and the distal end 176. The elongate section 178 is positioned in thepassageway 152 of the heat sink 31 and secured therein by closurebrackets 180. To be clear, in this embodiment, the closure brackets 180are not coupled to the SMA element 172; instead, the closure brackets180 close the passageway 152 to capture the elongate section 178therein. By contrast, the proximal end 174 and the distal end 176 of theSMA element 172 are fixed or anchored with respect to the module cage18. Thus, elongate section 178 can flex or deform with respect to theproximal end 174 and the distal end 176 and act on (e.g., push) theclosure brackets 180 and/or the heat sink 31 to move the heat sink 31(which moves with the closure brackets 180) with respect to the modulecage 18. In at least some embodiments, the elongate section 178 may becoated or covered with insulation, such as with a hot shrink tube, overmolding, or any other technique, so that electric current does not leakbetween the SMA element 172 and the heat sink 31 (and/or closurebrackets 180).

In the depicted embodiment, the closure brackets 180 are secured to themounting points 154 of the heat sink 31 with fasteners, but in otherembodiments, the closure brackets 180 can be secured to the fins 140 inany manner (e.g., welding, soldering, etc.). Additionally, in thedepicted embodiment, the proximal end 174 and the distal end 176 of theSMA element 172 are secured to the module cage 18 via support frame 190,but in other embodiments the proximal end 174 and the distal end 176 ofthe SMA element 172 could be secured directly to the module cage 18(e.g., the module cage 18 could include upwardly extending brackets thatprovide connection points).

That said, in the depicted embodiment, the support frame 190 includes afirst frame portion 192 and a second frame portion 194 that are coupledtogether around the module cage 18. Additionally, the first frameportion 192 and the second frame portion 194 can be coupled to the PCB16 and/or the module cage 18. Regardless, the first frame portion 192includes or defines a first mounting portion 196 above the module cage18 and the second frame portion 194 defines a second mounting portion198 above the module cage 18. Mounting portions 196 and 198 are orinclude insulated or non-conductive portions that can insulate SMAelement 172 from the module cage 18 and/or the remainder of heat sinkassembly 30. Alternatively, the entire support frame 190 can beinsulated or non-conductive. Either way, due to this insulation, currentdelivered to the SMA element 172 will not run into the heat sink 31, themodule cage 18, and/or a module 20 installed in the module cage 18.

Now referring to FIGS. 4 and 6, generally, SMA actuates (e.g., deformsand/or contracts) in response to heating. Consequently, the SMA element172 is included in or connected to circuitry 200 that can providecurrent to the SMA element 172 and cause resistive heating of the SMAelement 172. For example, in FIG. 4, the proximal end 174 and the distalend 176 of SMA element 172 are coupled to positive and negative poles ofa power source 202 via wires 204A and 204B (represented as wires 204 inFIG. 6) to form a circuitry 200 including the SMA element 172. The powersource 202 can be a dedicated battery or any power source included in orconnected to a computing solution in which the heat sink assembly 30 isinstalled. FIG. 6 illustrates this circuity schematically in combinationwith additional electrical elements.

Specifically, in FIG. 6, the circuitry 200 includes a switch 206 thatcan be closed to deliver current to the SMA element 172. The switch 206may be a mechanical switch actuated by a mechanical/physical actuator(e.g., a push button actuator) and/or an electrical/digital switch thatis actuatable by a processor. Either way, closing the switch 206 maydeliver current to the SMA element 172 that effectuates resistiveheating of the SMA element 172 to cause an actuation of the SMA element172 (e.g., a contraction or deformation). Additionally, in someembodiment, the circuitry 200 may include an indicator 210, such as alight, arranged in parallel with the SMA element 172. With such anarrangement, closing the switch 206 actuates the SMA element 172 and theindicator 210, for example, to provide an illuminated indication.However, this is just one example arrangement for an indicator andindicators could be arranged and operated in any manner now known ordeveloped hereafter. For example, circuitry 200 could have any otherconfiguration that allows indicator 210 to be activated in one or morecolors. Additionally or alternatively, circuitry 200, or portionsthereof, could be duplicated, to provide two or more indications (e.g.,raised and lowered). Circuitry 200 may also include a constant-currentfeature that helps enable protracted actuation of SMA element 172without exceeding thermal limits for the SMA material.

Now turning to FIG. 7, this Figure illustrates an actuation of SMAelement 172. The initial or rest state or position P1 of the SMA element172 is shown in dashed lines and the actuated state or position P2 isshown in solid lines. In this embodiment, SMA element 172 is a one-waySMA formed from any material that deforms when heated, including but notlimited to copper-aluminum-nickel (Cu—Al—Ni), nickel-titanium (Ni—Ti),iron-manganese-silicon (Fe—Mn—Si), copper-zinc-aluminum (Cu—Zn—Al), andother alloys of zinc, copper, gold, and iron. Generally, the deformationbehavior of a specific alloy can be modeled using hysteresis curves,which map material states of SMA as a function of temperature. Thus,specific alloy materials may be selected for SMA element 172 based onenvironmental characteristics of a computing solution in which the SMAelement 172 is to be included and/or the current that will be deliveredto the SMA element 172. For example, the SMA element 172 may be designedto actuate at a temperature that is significantly higher than atemperature of heat sink 31 during cooling operations to prevent heatingof the heat sink 31 from causing an actuation of the SMA element 172.

Moreover, regardless of the specific composition of the SMA element 172,the SMA element 172 can be trained with thermomechanical treatments nowknown or developed hereafter so that the SMA element 172 deforms tospecific shape when heated to a specific temperature (e.g., withresistive heating). For example, the SMA element 172 may be trained tomove vertically between positions P1 and P2. Additionally oralternatively, the SMA element 172 may be trained to move along onedegree of freedom (e.g., vertical, linear movement) and, thus, mayrestrict the heat sink assembly 30 to movement along one degree offreedom. Still further, the SMA element 172 can be trained to move inany direction and the heat sink assembly 30 might include additionalfeatures (e.g., guide pins) to control or restrict movement of the heatsink 31 (e.g., to one degree of freedom).

Still referring to FIG. 7, but now in combination with FIGS. 3A-6,regardless of how the SMA element 172 is trained or tuned, actuating theSMA element 172 presented herein may move the heat sink 31 verticallywith respect to a module cage 18 (and, if installed, a computing module20). For example, in the embodiment of FIGS. 2A-7, actuating the SMAelement 172 may contract the SMA element 172 and cause the elongatedsection 178 to move upwards along vertical axis A1. Upwards movement ofthe elongated section 178 along vertical axis A1 pushes the closurebrackets 180 upwards (see FIGS. 4 and 5) which may move the heat sink 31upwards (along vertical axis A1) with respect to the module cage 18(since the closure brackets 180 are fixedly secured to the heat sink31). More specifically, upwards movement of the elongated section 178along vertical axis A1 may move the heat sink 31 upwards a distance D1upwards along axis A1, creating a gap G (see FIG. 1A) of, for example,2-3 millimeters between the computing module 20 and the TIM 35. Notably,the proximal end 174 and the distal end 176 of the SMA element 172remain fixed or anchored during deformation of the SMA element 172 and,thus, the elongate section 178 can drive vertical movement of the heatsink 31, which is essentially floating on the SMA element 172 (or atleast on the elongate section 178 of the SMA element 172).

In the specific embodiment depicted in FIGS. 3A-7, the SMA element 172is a one-way SMA and, thus, provides movement in one direction (whenit's crystalline structure changes), but must be restored to itsoriginal or rest position (position P1) before it can provide anotheractuation. Thus, the biasing member 160 works in combination with thecircuitry 200 to control movement of the heat sink 31. In particular,the circuitry 200 delivers a current to the SMA element 172 to cause achange to the crystalline structure of SMA element 172 that contractsthe SMA element 172 to lift the heat sink 31 to its actuated position P2(e.g., to provide a gap G as shown in FIG. 1A). Then, since the biasingmember 160 is constantly exerting a restorative force on the heat sink31, the biasing member 160 will return the SMA element 172 to its restposition P1 when current is no longer to the SMA element 172. Thislowers the heat sink 31 into engagement with the module cage 18 and/or amodule 20 installed within the module cage 18. Thus, to maintain theheat sink 31 in a raised position, current must be continually deliveredto the SMA element 172. In fact, in at least some embodiment, thevoltage is continuously adjusted (in any manner now known or developedhereafter) to maintain a constant current across the SMA element 172when the heat sink 31 should be in a raised position (e.g., based on auser actuation and/or processor generated instructions).

Further, in at least some embodiments, the SMA element 172 may betrained, tuned, or controlled (e.g., controlled with current delivery)to provide non-constant vertical motion of the heat sink 31. This may beadvantageous, for example, to provide an initially rapid downward motionof the heat sink, followed by a more gradual “seating” of TIM 35 ontothe module 20. Alternatively, the tuning/training/controlling couldprovide a slow initial raising of the TIM 35 away from the module 20 toprevent the TIM 35 from being damaged when the TIM 35 is disconnectedfrom the module 20. Additionally or alternatively, the configurationshown in FIGS. 3A-7 could be reversed and actuation of the SMA element172 could compress the TIM 35 against a module 20. In such embodiments,the SMA element 172 can be trained to provide a specific compression ofthe TIM 35 to maximize heat transfer (e.g., tuned for a specific TIMmaterial), either in combination with or independent of additionalcomponents (e.g., spring clips) that create compression. Exampleembodiments including such an arrangement are discussed in furtherdetail below.

Overall, when the SMA element 172 is in its actuated position P2 (suchthat gap G is provided between the TIM 35 and the module cage 18), acomputing module 20 can be installed or removed from the module cage 18.In at least some embodiments, the gap G may be consistent across thesurface area of the TIM 35 (e.g., an area defined by W3 and L3), suchthat the TIM 35 (or at least a portion thereof) is parallel to themodule cage 18 and/or the computing module 20 (i.e., the heat sinkassembly 30 may provide uniform lifting). In any case, after a computingmodule 20 is installed in module cage 18 (which may be detected, forexample, in the manner discussed below in connection with FIG. 9), theSMA element 172 may be moved to its rest position P1 (e.g., by openingswitch 206 or otherwise stopping the flow of current to SMA element172), which may move the TIM 35 into engagement with a heat transfersurface of the computing module 20 (e.g., top surface 22). In fact, insome embodiments, moving the SMA element 172 to its rest position P1 maycompress the TIM 35 against the heat transfer surface of the computingmodule 20 (e.g., top surface 22), further encouraging heat transfer.

Now turning to FIG. 8-15B, these Figures depict additional embodimentsof the heat sink assembly presented herein, or at least of portionsthereof. In these Figures, components that are similar to componentsshown in FIGS. 2A-7 are labeled with like reference numerals and, anydescription of like reference numerals included above should beunderstood to apply to like components included in FIGS. 8-15B. Thus,for brevity, the foregoing description focuses on differences betweenthe embodiments. Additionally, if components of FIGS. 2A-7 are not shownin embodiments depicted in FIGS. 8-15B, these embodiments maynevertheless be described with reference to components of FIGS. 2A-7 toprovide clarity and/or context.

That said, FIGS. 8 and 9 depict a heat sink assembly 30 that can beactuated in response to a physical/mechanical actuator. FIG. 8illustrates an example actuator 220 that may be included on a frontpanel 100 of computing apparatus 12 in combination with exampleindicators 210A and 210B. Notably, since FIG. 8 depicts two indicators210A and 210B, the circuitry of this embodiment may be modified ascompared to the circuitry 200 shown in FIG. 6. FIG. 9 illustrates amethod 250 of operating indicators 210A and 210B. As is described indetail below, indicators 210A and 210B may be operated based onactuations of actuator 220 and/or electrical actuations (e.g., based oncommands generated by a processor). That is, with this arrangement,processing logic may control operations of indicator 210A, indicator210B, and/or SMA element 172, either in combination with actuations ofactuator 220 or independent of actuations of actuator 220. In fact, insome embodiments, the computing solution need not include an actuatorand a processor 248 could execute instructions stored in memory 249 tocontrol indicator 210A, indicator 210B, and/or SMA element 172 (or anyother arrangement of indicators and SMA elements) with purely electricaloperations.

In FIG. 9, method 250 illustrates operations that processor 248, whichmay comprise any processor included in the computing solution of FIG. 8may execute to control indicator 210A, indicator 210B, and/or SMAelement 172 (or any other arrangement of indicators and SMA elements).Generally, the processor 248 may comprise one or more processing coresand the memory 249 may comprise at least one non-transitory computerreadable medium or memory for holding instructions programmed accordingto the embodiments presented, for containing data structures, tables,records, etc. Instructions stores in memory 249 may include softwarecode scripts, etc. for controlling indicators and/or the SMA element172. In any case, initially, at 252, the processor 248 determines if anunlock command has been received. In some instances, the unlock commandcan be the actuation of actuator 220. Alternatively, an unlock commandcould be a command input or generated via a graphical user interface orother computing interface connected to processor 248. In response tosuch a command, electrical circuitry of the SMA element 172 is enabled.That is, current is delivered to SMA element 172 (e.g., by power source202). This actuates (e.g., deforms/contracts) the SMA element 172 andlifts the heat sink 31 in the manner described above.

Then, at 256, the processor monitors the current and maintains aconstant current across the SMA element 172 by adjusting the voltage, aswas discussed above. During operations 254 and/or 256, the processor 248can activate indicator 210B, for example, to provide a green lightindication that the module cage 18 is “OPEN,” as is shown at 258.Additionally or alternatively, as mentioned above, an actuation ofactuator 220 might close a switch that activates indicator 210B orallows processor 248 to activate indicator 210B.

Once the module cage is “OPEN,” the processor 248 may, at 260, monitorfor presence of a module 20 in the module cage 18. That is, once theheat sink 31 is in a raised position, the processor 248 may monitor forpresence of a module 20 in the module cage 18 at 260. For example, themodule cage 18 may include an interrupt at or adjacent its back end 122that provides a signal when a module 20 is fully installed in the modulecage 18. Additionally or alternatively, the processor 248 can monitorconnector 124 to sense when the connector 25 of the module 20 has beenfully inserted into the module cage 18 and connected with connector 124.Still further, in some embodiments, a user might be able to actuate theactuator 220 a second time to indicate that a module 20 has been fullyinstalled in the module cage 18. Regardless, the processor 248 mayensure that the SMA element 172 stays activated (maintaining the heatsink 31 in a raised position) until the module 20 is detected as beinginstalled in the module cage 18. That is, the processor 248 may causethe power source 202 to continue delivering power to SMA element 172(with continued instructions or by withholding a command to cut offpower) until a module 20 is determined to be fully installed in modulecage 18.

When processor 248 determines that a module 20 is fully installed in themodule cage 18, the processor 248 may, at 262, disable electricalcircuitry of the SMA element 172. That is, the processor 248 maydisconnect power from the SMA element 172 to discontinue the delivery ofcurrent to SMA element 172 (e.g., by providing instructions to powersource 202). This may deactivate the SMA element 172 and allow biasingmember 160 to move the heat sink 31 into contact with the module 20and/or the module cage 18. Additionally, indicator 210A can be activated(while indicator 210B is deactivated), for example, to provide a redlight indication that the module cage 18 is “LOCKED,” as is shown at264. The heat sink assembly 30 may then remain in a locked positionuntil a new unlock command is received at 252.

Next, FIGS. 10A and 10B illustrate another example embodiment of a heatsink assembly 30′ presented herein. Heat sink assembly 30′ issubstantially similar to the heat sink assembly 30 shown in at leastFIG. 3A. Thus, to reiterate, like reference numerals are used to denotesimilar parts and, for brevity, the foregoing description focuses ondifferences between the embodiments. Most notably, in this embodiment,the heat sink assembly 30′ does not include a support frame. Instead,the proximal end 174 of the SMA element is connected to the front panel100 of the apparatus 12 and the distal end 176 is connected to a bracket276 extending from the module cage 18. Moreover, the SMA element 172 isnot secured within the heat sink 31 by covers, such as closure brackets180 and, instead, is directly connected to heat sink 31 via one or moreinsulated couplings 279. Still further, heat sink assembly 30′ does notinclude a biasing member 160 in the form of a spring clip, but instead,includes compression springs 160′ that exert a constant restorative orbiasing force BF (see FIG. 10B) on the heat sink 31 and SMA element 172(like biasing member 160).

Despite the differences between heat sink assembly 30 and heat sinkassembly 30′, heat sink assembly 30′ still operates in a substantiallysimilar manner to heat sink assembly 30. That is, SMA element 172 isstill a one-way SMA that contracts to an actuated position P2 and liftsthe heat sink along axis A1 a distance D1 to a raised position P4 (seeFIG. 10B) in response to resistive heating. This creates a gap G thatallows a module 20 to be inserted or removed from cage 20 withoutdamaging TIM 35. Then, when power to the SMA element 172 is turned off,the biasing force BF of compression springs 160′ returns the SMA element172 to its rest position P1 while lowering the heat sink 31 into alowered position P3 where it can compress TIM 35 against a module 20(see FIG. 10A). Additionally, like previously described embodiments,heat sink assembly 30′ includes an actuator 220 and indicator 210 thatcan actuate the heat sink assembly 30′ and provide indications of howthe heat sink 31 is positioned, respectively.

Still referring to FIGS. 10A and 10B, but now with reference to FIGS.11A and 11B as well, in this embodiment, the heat sink assembly 30′ alsoincludes a locking feature that can prevent insertion or removal of themodule 20 when the heat sink assembly 30′ is in its lowered position P3.Specifically, in this embodiment, the heat sink assembly 30′ includes aprotrusion 282 positioned forwardly of the TIM 35 on the mating surface133 of the heat sink 31 (e.g., closer to the open front end 120 of themodule cage 18), as is shown clearly in FIG. 11A. With this embodiment,and as is shown in FIG. 11B, the computing module 20 includes acorresponding receptacle 284 configured to mate with the protrusion 282when the computing module 20 is fully installed into a module cage 18.Thus, when the heat sink assembly 30′ moves the TIM 35 into engagementwith the top surface 22 of the computing module 20, the protrusion 282will engage the receptacle 284 and resist movement in the front-to-backdirection. Then, if the computing module 20 is pulled outwardly prior tothe heat sink assembly 30 moving the TIM 35 out of engagement with thetop surface 22 of the computing module 20, the protrusion 282 and thereceptacle 284 may resist this movement and prevent damage to the TIM 35that can occur when the module 20 slides along the TIM 35. Thisarrangement will also ensure that module 20 is not forcefully insertedor extracted which could cause an unintentional damage for the TIM 35(insertion prevention is illustrated in FIG. 10A).

Next, FIGS. 12, 13, 14A, and 14B illustrate yet further exampleembodiments of the heat sink assembly presented herein that can operatewithout a biasing member exerting a constant restorative force on theheat sink 31. First, FIG. 12 provides a heat sink assembly 30(2) with abi-stable toggle element 300 disposed between two one-way SMA elements:SMA element 172A and SMA element 172B. When current is delivered to oneof SMA element 172A and SMA element 172B, that SMA element may deform(e.g., contract) and move the bi-stable toggle element 300 to a firstposition. Then, when current is delivered to the other of SMA element172A and SMA element 172B, that SMA element may deform (e.g., contract)and move the bi-stable toggle element 300 to a second position.Alternatively, SMA element 172A and SMA element 172B may have differentcompositions and/or characteristics (e.g., different “training” or“tuning”) that cause the different SMA elements to respond (e.g., deformor actuate) to different magnitudes of currents (and, thus, might beactuated by precisely controlling the current delivered to both SMAelements). Regardless, with this arrangement, actuation of one of SMAelement 172A and SMA element 172B drives the bi-stable toggle element300 to a specific position and then the bi-stable toggle element 300holds or locks the heat sink 31 in that position. Consequently, currentneed not be constantly delivered to SMA element 172A or SMA element 172Bto hold (e.g., lock) the heat sink assembly 30(2) in a specific position(e.g., a raised or lowered position).

More specifically, in the depicted embodiment, delivering current to SMAelement 172B may contract SMA element 172B, pivoting a bottom end ofpivot points 302 inwards and moving (e.g., snapping) the bi-stabletoggle element 300 to position P5 (shown in solid lines). Pivoting pivotpoints 302 will also stretch or elongate SMA element 172A (i.e., returnSMA element 172A to its rest position) so that SMA element 172A is readyto actuate (e.g., contract) in response to receiving current. In thedepicted embodiment, bi-stable toggle element 300 is coupled to heatsink 31 at pivot point 302. Thus, moving the bi-stable toggle element300 to position P5 moves the heat sink upwards a distance D1. However,in other embodiments, the bi-stable toggle element 300 may be directlycoupled to and/or enclosed within the heat sink 31 in any manner.Regardless, once the bi-stable toggle element 300 is in position P5,current need not be delivered to SMA element 172B, as the bi-stabletoggle element 300 will maintain (e.g., lock) the heat sink 31 in araised position.

Then, to lower the heat sink 31, current is delivered to SMA element172A to actuate (e.g., contract) SMA element 172A and pivot top ends ofpivot points 302 inwards. This moves (e.g., snaps) the bi-stable toggleelement 300 to position P6 (shown in dashed lines) and moves the heatsink downwards a distance D1. Again, once the bi-stable toggle element300 is in position P6, current need not be delivered to SMA element172A, as the bi-stable toggle element 300 will maintain (e.g., lock) theheat sink 31 in a lowered position.

FIG. 13 illustrates another example embodiment of a heat sink assemblythat can operate without a biasing member exerting a constantrestorative force on the heat sink 31. Heat sink assembly 30(3) includestwo SMA elements, like heat sink assembly 30(2) of FIG. 12, but providesa first SMA element 172C trained to deform to a shape that raises theheat sink 31 and a second SMA element 172D trained to deform to a shapethat lowers the heat sink 31. For example, SMA element 172C may betrained and/or arranged so that actuation of SMA element 172C arcs orbends SMA element 172C upwards. SMA element 172C is connected to heatsink 31 at connection points 179C and, thus, upward bending or arcing ofSMA element 172C moves heat sink 31 upwards. Meanwhile, SMA element 172Dmay be trained and/or arranged so that actuation of SMA element 172Darcs or bends SMA element 172D downwards. SMA element 172D is connectedto heat sink 31 at connection points 179D and, thus, downward bending orarcing of SMA element 172D moves heat sink 31 downwards. However, SMAelements 172C and 172D are only shown directly attached to heat sink 31as an example and SMA elements 172C and 172D could be coupled to heatsink 31 in any manner provided that actuation (e.g., contraction) of SMAelement 172C or 172D moves the heat sink 31 up or down.

Now turning to FIGS. 14A and 14B, these Figures depict yet anotherexample embodiment of a heat sink assembly that can operate without abiasing member exerting a constant restorative force on the heat sink31. Heat sink assembly 30(4) is substantially similar to the heat sinkassembly 30′ shown in FIGS. 10A and 10B; however, now the heat sinkassembly 30(4) does not include compression springs 160′ or any kind ofbiasing member 160. Instead, SMA element 172E is a two-way SMA element.Thus, in response to a first current being delivered to a first portionof the SMA element 172E, the SMA element 172E may lift heat sink 31 adistance D1 along a vertical axis A1 to a raised position P4 (see FIG.14B). Then, in response to a current being delivered to a second portionof the SMA element 172E, the SMA element 172E may lower heat sink 31 adistance D2 (which may be equal to distance D1) along a vertical axis A1to a lowered position P3 (see FIG. 14A). Alternatively, differentmagnitudes of current might cause SMA 172E to raise and lower.Regardless, the arrangement shown in FIGS. 14A and 14B is similar to thearrangement of heat sink assembly 30(3) of FIG. 13, but now thefunctionality of SMA elements 172C and 172D from FIG. 13 is achieved bya single SMA element 172E.

Notably, with this embodiment, the currents that actuate SMA element172E may move the SMA element 172E between a first actuated position P7(corresponding to lowered position P3 of heat sink 31) and a secondactuated position P8 (corresponding to raised position P4 of heat sink31). However, since a restorative force (e.g., a biasing force) is notconstantly acting on the heat sink 31 of heat sink assembly 30(4), SMAelement 172E need not receive a constant current to stay in positions P7and P8. Instead, current can be delivered to SMA element 172E to movethe SMA element 172E between positions P7 and P8 and can be turned offafter an actuation (like the embodiments shown and described inconnection with FIGS. 12 and 13).

Now turning to FIGS. 15A and 15B, but with continued reference to FIGS.14A and 14B, generally, two-way SMA toggles between two different shapesor “conformations.” To achieve this, SMA element 172E includes twoopposing SMA layers or SMA wires 172E(1) and 172E(2) that are joined andseparated by a flexible and heat resistant material 172E(3). The SMAwires 172E(1) and 172E(2) and the heat resistant material 172E(3) extendlongitudinally along a length of SMA element 172E and may be containedwithin an outer casing (giving SMA element 172E the appearance of asingle wire). The first SMA layer/wire 172E(1) and the second SMAlayer/wire 172E(2) are each trained or programmed to attain a specificshape when heated. That is, SMA layers/wires 172E(1) and 172E(2) mayeach be or function like one-way SMAs and, thus, any description ofone-way SMAs included herein (e.g., relating to composition or training)should be understood to apply to SMA layers/wires 172E(1) and 172E(2).Consequently, to actuate SMA element 172E, current may be appliedindependently and sequentially to SMA layer/wire 172E(1) and 172E(2) totoggle the configuration of SMA element 172E between two configurationsor states. Additionally or alternatively, first SMA layer/wire 172E(1)and the second SMA layer/wire 172E(2) may have different compositionsthat respond to different currents. FIG. 15A illustrates (in anexaggerated fashion) contraction of first SMA layer/wire 172E(1) drivingSMA element 172E to its first actuated position P7 and FIG. 15Billustrates (in an exaggerated fashion) contraction of second SMAlayer/wire 172E(2) driving SMA element 172E to its second actuatedposition P8.

Now turning to FIGS. 16 and 17, these Figures illustrate examplesolutions that can utilize the heat sink assembly 30 presented herein.First, in FIG. 16, system 400 is a server or switch assembled in anapparatus 12 that is a pizza-box style chassis. The apparatus 12includes a cage to receive a module 20 in the form of a modular portadapter (MPA). This provides flexibility for customer-basedspecializations and the heat sink assembly 30 presented herein canprovide cooling for any MPA. Second, FIG. 17 illustrates a solution 500with an apparatus 12 in the form of an MPA that can support computingmodules 20 in the form of CFP2 optical transceivers. In this instance,the heat sink assembly 30 can be installed in the MPA to provide coolingfor the CFP2 optical transceivers. Then, if the MPA was installed in,for example, a line card, the line card might also include a heat sinkassembly 30 formed accordance with the embodiments presented herein tocool the MPA within the line card.

Among other advantages, the heat sink assembly presented herein mayimprove cooling of computing modules while minimizing a footprint ofcooling components (at least because a heat sink may cover an entirecomputing module without moving beyond a lateral periphery of acomputing module). In fact, in at least some embodiments, the heat sinkassembly presented herein may completely eliminate the need for anactuator and leave the front panel unobstructed with any actuators.These embodiments may utilize a purely electrical actuation of the heatsink assembly. Alternatively, the heat sink assembly may provide a smallbutton that requires only a push actuation and, thus a computingsolution need not be installed or manufactured in a manner that providesspace to accommodate linear or rotational movement of a user's hand atthe front panel.

In FIG. 18, diagram 600 illustrates the temperature improvementsprovided by the heat sink assembly 30 as compared to a heat sink 31 thatis not modified to support the actuation assembly 170 of heat sinkassembly 30 (e.g., a heat sink 31 of the same size, but without thefeatures (including the TIM 35) of heat sink assembly 30 describedherein). Notably, the heat sink assembly 30 presented herein achieveslower temperatures under the same airflow conditions. For example, theheat sink assembly 30 may cool a module case to 70 degree Celsius withapproximately 9 cubic feet per minute (CFM) of airflow while theunmodified heat sink requires approximately 12 CFM to achieve the sametemperature. Thus, the heat sink assembly 30 may provide approximately25% improvement.

Moreover, the thermal data from diagram 600 indicates that the heat sinkassembly 30 does not induce thermal spreading that mitigatesimprovements in contact resistance provided by the TIM 35 engaging thecomputing module 20. That is, forming passageway 152 and/or corners 145in/on heat sink 31 will not generate thermal spreading that counteractsthe thermal effectiveness of the heat sink 31. Thus, the heat sinkassembly presented herein may support higher operational temperatureswhile still meeting regulatory standards. Additionally or alternatively,the heat sink assembly presented herein may reduce operatingtemperatures which may lower power consumption (e.g., due to reduced fanspeeds) and/or reduce acoustic noise (e.g., from fans). The heat sinkassembly presented herein may also achieve these advantages with aninexpensive solution that, for example, does not require expensive andmaintenance intensive spring clips.

In summary, an apparatus is provided comprising: a cage defining achamber; a heat sink to facilitate heat dissipation, the heat sinkincluding a mating surface; a thermal interface material including afirst surface and a second surface, the first surface being coupled tothe mating surface of the heat sink and the second surface beingopposite the first surface so that the second surface can be positionedagainst a perimeter of the chamber; and an actuation assembly includinga shape memory alloy (SMA) element, wherein when the SMA element is in afirst position, the second surface of the thermal interface material isdisposed within or adjacent the perimeter of the chamber, and when theSMA element is moved to a second position, the second surface of thethermal interface material is moved a distance away from the perimeterof the chamber.

In another form, a heat sink assembly for a cage for a field replaceablecomputing module is provided, comprising: a heat sink to facilitate heatdissipation, the heat sink including a mating surface; a thermalinterface material including a first surface and a second surface, thefirst surface being coupled to the mating surface of the heat sink andthe second surface being opposite the first surface so that the secondsurface can engage a heat transfer surface of the field replaceablecomputing module installed adjacent the heat sink; and an actuationassembly including a shape memory alloy (SMA) element, wherein when theSMA element is in a first position, the second surface of the thermalinterface material contacts the heat transfer surface of the fieldreplaceable computing module, and when the SMA element moves to a secondposition, the second surface of the thermal interface material is moveda distance away from the heat transfer surface of the field replaceablecomputing module.

In yet another form, a system is provided, comprising: a cage defining achamber sized to receive the field replaceable computing module with aheat transfer surface; a heat sink to facilitate heat dissipation, theheat sink including a mating surface; a thermal interface materialincluding a first surface and a second surface, the first surface beingcoupled to the mating surface of the heat sink and the second surfacebeing opposite the first surface so that the second surface canselectively engage the heat transfer surface of the field replaceablecomputing module when the field replaceable computing module isinstalled in the chamber of the cage; and an actuation assemblyincluding a shape memory alloy (SMA) element, wherein when the fieldreplaceable computing module is installed in the chamber of the cage andthe SMA element is in a first position, the second surface of thethermal interface material contacts the heat transfer surface of thefield replaceable computing module, and when the SMA element moves to asecond position, the second surface of the thermal interface material ismoved a distance away from the heat transfer surface of the fieldreplaceable computing module.

The above description is intended by way of example only. Although thetechniques are illustrated and described herein as embodied in one ormore specific examples, it is nevertheless not intended to be limited tothe details shown, since various modifications and structural changesmay be made within the scope and range of equivalents of the claims. Inaddition, various features from one of the embodiments may beincorporated into another of the embodiments. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the disclosure as set forth in thefollowing claims.

It is also to be understood that the heat sink assembly, apparatus, andsystem presented herein described herein, or portions thereof, may befabricated from any suitable material or combination of materials, suchas plastic, metal, foamed plastic, wood, cardboard, pressed paper,supple natural or synthetic materials including, but not limited to,cotton, elastomers, polyester, plastic, rubber, derivatives thereof, andcombinations thereof. Suitable plastics may include high-densitypolyethylene (HDPE), low-density polyethylene (LDPE), polystyrene,acrylonitrile butadiene styrene (ABS), polycarbonate, polyethyleneterephthalate (PET), polypropylene, ethylene-vinyl acetate (EVA), or thelike.

Finally, when used herein, the term “approximately” and terms of itsfamily (such as “approximate,” etc.) should be understood as indicatingvalues very near to those that accompany the aforementioned term. Thatis to say, a deviation within reasonable limits from an exact valueshould be accepted, because a skilled person in the art will understandthat such a deviation from the values indicated is inevitable due tomeasurement inaccuracies, etc. The same applies to the terms “about” and“around” and “substantially.”

What is claimed is:
 1. An apparatus comprising: a cage defining achamber; a heat sink to facilitate heat dissipation, the heat sinkincluding a mating surface; a thermal interface material including afirst surface and a second surface, the first surface being coupled tothe mating surface of the heat sink and the second surface beingopposite the first surface to be positioned against a perimeter of thechamber; and an actuation assembly including a shape memory alloy (SMA)element configured to be moveable between a first position and a secondposition such that when the SMA element is in the first position, thesecond surface of the thermal interface material is disposed within oradjacent the perimeter of the chamber, and when the SMA element is movedto the second position, the second surface of the thermal interfacematerial is moved a distance away from the perimeter of the chamber. 2.The apparatus of claim 1, wherein the second surface of the thermalinterface material is substantially parallel to a top of the perimeterof the chamber when the SMA element is in the second position.
 3. Theapparatus of claim 2, wherein the heat sink is moveable with one degreeof freedom when the SMA element moves between the first position and thesecond position.
 4. The apparatus of claim 2, wherein the heat sinkspans a front-to-back dimension of the chamber.
 5. The apparatus ofclaim 1, wherein the SMA element is a one-way SMA and the actuationassembly further comprises: a biasing member configured to move the SMAelement to the second position.
 6. The apparatus of claim 1, wherein theSMA element is a two-way SMA and is configured to move between the firstposition and the second position in response to different magnitudes ofcurrent or in response to current being delivered to different portionsof the SMA element.
 7. The apparatus of claim 1, wherein the SMA elementis a first SMA element and the actuation assembly further comprises: asecond SMA element, wherein the first SMA element is configured todeform to move to the first position and the second SMA element isconfigured to deform to drive movement of the first SMA element to thesecond position.
 8. The apparatus of claim 7, wherein the actuationassembly further comprises: a bi-stable toggle that is configured tolock the thermal interface material in specific positions after thethermal interface material is moved by the first SMA element or thesecond SMA element.
 9. The apparatus of claim 1, further comprising: atleast one indicator that provides an indication of a position of thethermal interface material.
 10. The apparatus of claim 1, wherein thethermal interface material is configured to selectively engage a heattransfer surface of a field replaceable computing module installed inthe chamber of the cage, such that the second surface of the thermalinterface material contacts the heat transfer surface of the fieldreplaceable computing module when the SMA element is in the firstposition and is spaced apart from the heat transfer surface of the fieldreplaceable computing module when the SMA element is in the secondposition.
 11. The apparatus of claim 1, wherein the actuation assemblyis configured to be actuated in response to solely electrical actuation.12. A heat sink assembly for a cage for a field replaceable computingmodule, comprising: a heat sink to facilitate heat dissipation, the heatsink including a mating surface; a thermal interface material includinga first surface and a second surface, the first surface being coupled tothe mating surface of the heat sink and the second surface beingopposite the first surface to engage a heat transfer surface of thefield replaceable computing module installed adjacent the heat sink; andan actuation assembly including a shape memory alloy (SMA) element,wherein when the SMA element is configured to be moveable between afirst position and a second position such that when the SMA element isin the first position, the second surface of the thermal interfacematerial contacts the heat transfer surface of the field replaceablecomputing module, and when the SMA element moves to the second position,the second surface of the thermal interface material is moved a distanceaway from the heat transfer surface of the field replaceable computingmodule.
 13. The heat sink assembly of claim 12, wherein the secondsurface of the thermal interface material is substantially parallel tothe heat transfer surface of the field replaceable computing module whenthe SMA element is in the second position.
 14. The heat sink assembly ofclaim 13, wherein the heat sink is moveable along one degree of freedomwhen the SMA element moves between the first position and the secondposition.
 15. The heat sink assembly of claim 12, wherein the heat sinkassembly further comprises: a passageway extending through the heatsink, the SMA element extending through the passageway.
 16. The heatsink assembly of claim 15, wherein the heat sink assembly furthercomprises: closure brackets configured to enclose the SMA element withinthe passageway.
 17. The heat sink assembly of claim 15, wherein the SMAelement is directly connected to the heat sink within the passageway.18. The heat sink assembly of claim 12, wherein the SMA element is aone-way SMA and the actuation assembly further comprises: a biasingmember configured to move the SMA element to the second position.
 19. Asystem comprising: a cage defining a chamber configured to receive afield replaceable computing module with a heat transfer surface; a heatsink to facilitate heat dissipation, the heat sink including a matingsurface; a thermal interface material including a first surface and asecond surface, the first surface being coupled to the mating surface ofthe heat sink and the second surface being opposite the first surface toselectively engage the heat transfer surface of the field replaceablecomputing module when the field replaceable computing module isinstalled in the chamber of the cage; and an actuation assemblyincluding a shape memory alloy (SMA) element, wherein when the fieldreplaceable computing module is configured to be installed in thechamber of the cage and configured to be moveable between a firstposition and a second position such that when the SMA element is in thefirst position, the second surface of the thermal interface materialcontacts the heat transfer surface of the field replaceable computingmodule, and when the SMA element moves to the second position, thesecond surface of the thermal interface material is moved a distanceaway from the heat transfer surface of the field replaceable computingmodule.
 20. The system of claim 19, further comprising: circuitryconfigured to activate a light to provide an illuminated indication whenthe SMA element is in at least one of the first position or the secondposition.